Blood pump with splitter impeller blades and splitter stator vanes and related methods

ABSTRACT

A rotordynamic pump for delivering continuous flow of fluids, such as blood, is provided. In one embodiment, the pump includes a stator housing having an inlet and an outlet. A rotor hub is disposed within the stator housing having a mixed-stage or mixed-flow impeller. The mixed flow impeller includes both principle blades and splitter blades, the splitter blades exhibiting a shorter axial length than the principle blades. One or more stator vanes and extend radially inwardly from the stator housing. The splitter blades and principle blades are arranged in a circumferentially alternating pattern. The stator vanes include principle stator vanes and splitter stator vanes, the splitter stator vanes exhibiting a shorter axial length than the principle stator vanes. The splitter vanes and principle vanes are arranged in a circumferentially alternating pattern. The rotor hub may be magnetically suspended and rotated within the stator housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 61/394,220, filed Oct. 18, 2010, and entitled BLOOD PUMP WITH SPLITTER IMPELLER BLADES AND SPLITTER STATOR BLADES. This application also claims priority to U.S. Provisional Patent Application No. 61/394,213 filed Oct. 18, 2010, entitled BLOOD PUMP WITH SEPARATE MIXED-FLOW AND AXIAL FLOW IMPELLER STAGES. The disclosures of the above referenced priority applications are incorporated by reference herein in their entireties.

TECHNICAL FIELD

This invention relates generally to pumps. More specifically, this invention relates to blood pumps, such as cardiac assist pumps that may be implanted in a patient.

BACKGROUND OF THE INVENTION

Rotordynamic pumps, such as centrifugal, mixed-flow, and axial-flow pumps with mechanical bearings or magnetically suspended systems, have been widely used as ventricular assist devices to support patients with heart diseases. In magnetically levitated blood pumps, which generally include an impeller that is both magnetically suspended and rotated without mechanical means, an annular gap located between the rotor and stator suspension and drive components is conventionally designed to be relatively small. A narrow annular flow gap generally necessitates higher rotational speeds of the rotor in order to generate the desired pressure rise and flow rates needed to support patients. One adverse outcome of operating a rotor at high rotational speeds is a tendency for high turbulence flow characteristics within the blood (e.g., high shear stress) that increase the extent and rate of red blood cell damage. This is a challenge in developing a long-term implantable ventricular assist device. Additionally, it is desirable to provide such a pump that is able to generate a wide range of flow rate and sufficient pressure rise with high efficiency and smooth operation, and very low level of blood damage. While one can design a pump that operates adequately at nominal flow conditions using modern design methods and analysis tools such as computer-aided-design (CAD) and computational fluid dynamics (CFD), flow separations, vortices and unsteady stalls can still occur at off-design conditions in conventional designs.

Additionally, for centrifugal or mixed-flow blood pumps with shrouded impellers (i.e., a circumferentially revolved surface interconnecting the impeller blade tips), the fluid within the clearance space between a rotating front shroud and the stationary housing can demonstrate a complex three-dimensional structure, leading to retrograde leakage flow and strong disk friction loss. The combination of disk friction loss and the strong vortical flow not only lowers pump efficiency but also potentially induces hemolysis and thrombosis. A similar flow pattern can also occur at the back clearance space between a rotating back shroud and the stationary housing for centrifugal or mixed flow pumps with or without a front shroud. The level of shear stress within the clearance between the walls of a shroud and housing depends, at least in part, on the pump rotational speed.

For centrifugal or mixed-flow blood pumps with unshrouded or semi-open impellers, the lack of a front shroud introduces a problem due to the blade tip leakage flow from pressure-side to suction-side of the blades which occurs through the clearance between the rotating blade tip and the stationary housing. The leakage flow can also generate a jet leakage vortex that interacts with the primary flow, causing hydraulic loss and possibly inducing blood trauma. The shear stress exhibited in the gap or clearance between the blade tip gap and the stationary housing is very sensitive to the pump rotational speed as well as the magnitude of the gap itself.

At some off-design conditions, undesirable flow patterns such as flow separation, vortices, retrograde flow, and inlet pre-rotation can occur in all types of rotordynamic pumps. Impeller inlet and discharge recirculation can also occur at some off-design conditions. For example, impeller exit recirculation can occur on the shroud side as well as on the hub side. All these undesirable flow patterns not only cause hydraulic losses, but may also induce hemolysis and thrombosis. At some other off-design conditions, unsteady flow patterns such as surge can occur. A surge usually includes strong pressure and mass flow oscillations which vary over time. Such an unsteady flow pattern not only has a significant effect on the pump efficiency and potential blood damage, but also may have a strong impact on the stability of the pump operation.

In blood pumps having a mixed-flow impeller used in conjunction with a magnetically levitated and rotated design, the impeller can utilize centrifugal force in a greater extent to convert kinetic energy into potential energy (pressure rise). However, undesirable steady and unsteady flow patterns such as flow separation, vortices, inlet and outlet recirculation, and surge can also occur at impeller and stator blades region at off-design conditions. In particular at some off-design condition such as high flow rate operation, an unsteady surge can cause unstable operation of the pump.

SUMMARY OF THE INVENTION

Various embodiments of rotordynamic pumps for fluids are set forth herein in accordance with the present invention.

In accordance with one embodiment of the present invention, a pump for delivering continuous flow of fluids is provided. The pump includes a stator housing having an inlet and an outlet and a rotor hub disposed within the stator housing between the inlet and the outlet. The rotor hub includes a body having a leading portion position adjacent the inlet, a trailing portion positioned adjacent the outlet, and at least one impeller blade positioned at the leading portion. The pump further includes at least one principle stator vane extending radially inward from the stator housing and positioned between the inlet and outlet. At least one splitter vane is positioned adjacent the at least one principle stator vane, the at least one splitter vane exhibiting an axial length that is shorter than the at least one principle vane.

In accordance with one embodiment, the at least one principle stator vane includes a plurality of principle stator vanes, the at least one splitter vane includes a plurality of splitter vanes, and the plurality of principle vanes and the plurality of splitter vanes are arranged in a circumferentially alternating pattern.

In one embodiment, the at least one impeller blade includes a plurality of impeller blades configured to provide both centrifugal flow and axial flow to fluid flowing therethrough. The impeller blades may include at least one principle blade and at least one splitter blade, the at least one splitter blade being axially shorter than the at least one principle blade. Additionally, the at least one principle blade may include a plurality of principle blades, the at least one splitter blade may include a plurality of splitter blades, and the plurality of principle blades and the plurality of splitter blades may be arranged in a circumferentially alternating pattern.

In one embodiment, a leading edge of each of the plurality of splitter vanes is positioned axially closer to the outlet than a leading edge of each of the plurality of principle vanes. Additionally, a leading edge of each of the plurality of splitter blades may be positioned axially closer to the outlet than a leading edge of each of the plurality of principle blades.

In one embodiment, the pump may include a shroud coupled with and at least partially enclosing the plurality of principle blades and the plurality of splitter blades.

In one embodiment, the trailing edge of each of the plurality of the principle blades axially coincides with a trailing edge of each of the plurality of splitter blades. Additionally, the trailing edge of each of the plurality of the principle vanes may axially coincide with a trailing edge of each of the plurality of splitter vanes.

In one embodiment, the rotor hub is configured to be magnetically suspended and rotated within the stator housing. Such an embodiment may be configured from materials that are blood and biologically compatible such that the pump may be configured as a blood pump and may be implanted within a patient.

In accordance with another embodiment of the present invention, another pump for delivering continuous flow of fluids is provided. The pump includes a stator housing having an inlet and an outlet and a rotor hub disposed within the stator housing between the inlet and the outlet. The rotor hub includes a body having a leading portion position adjacent the inlet, a trailing portion positioned adjacent the outlet, a plurality of principle impeller blades, and a plurality of splitter impeller blades, each of the plurality of splitter blades being axially shorter than each of the plurality principle blades. The plurality of splitter blades and the plurality of principle blades are arranged in an alternating circumferential pattern about the leading portion of the body. A plurality of principle stator vanes extend radially inward from the stator housing and are positioned between the inlet and outlet. A plurality of splitter stator vanes extend radially inward from the stator housing, wherein each of the plurality of splitter vanes exhibit an axial length that is shorter than each of the plurality of principle vanes.

In accordance with another embodiment of the present invention, a method of manufacturing a pump is provided. The method comprises providing a stator housing having an inlet and an outlet; providing a rotor hub having a mixed-flow impeller near a leading portion of the rotor hub; positioning the rotor hub within the stator housing to define an annular flow path through the stator housing; providing at least one principle stator vane extending from the stator housing; providing at least one splitter stator vane extending from the stator housing adjacent the at least one principle stator vane, the at least one splitter vane having an axial length that is shorter than the at least one principle vane.

In various exemplary embodiments, there may be provided a rotordynamic apparatus and method suitable long-term implantation into humans for artificial circulatory support. In one embodiment, there may be provided a rotordynamic blood pump and method including a flow path geometry characterized with high hydraulic efficiency, low power consumption, uniform flow fields, smooth operation, and low blood damage at both nominal flow and off-design conditions.

In another embodiment, there may be provided a rotordynamic blood pump suitable for easy arrangements of magnetic suspension and drive components along the annular portion of the flow path.

Exemplary embodiments may provide an apparatus and method for a fluid pump for pumping bloods and other fluids, which integrates a mixed-flow or high-specific speed centrifugal impeller having at least one impeller stage including both principle blades and shorter splitter blades spaced between the principle blades, and a stator having at least one stage of blades fitted with both principle and shorter splitter blades near the outflow end of the pump. The rotating impeller stage includes principle blades of a conventional length and in between the same number of shorter splitter blades arranged in an alternating circular pattern along the diverging inlet end of the rotor. The stator stage with one or more principle stator blades and the equivalent number of shorter splitter blades arranged alternatively in circumferential direction displaced on the rear converging surface of the stator housing.

High efficiency, low blood damage, and smooth operation at design and off-design conditions are the critical requirements for a long term implantable blood pump. High efficiency is accomplished with the inclusion of splitter blades for both impeller and stator. The leading edges of both the impeller and stator shorter splitter blades are staggered with respect to principle blades, and initiate subsequently to the leading edge of the principle blades and overlap a portion of the principle blades wherein both principle and splitter blades preferably terminate at the same position in meridional section. Such an arrangement lessens the flow blockage at the impeller inlet side, thus improving the uniformity of flow field at the impeller inlet region by preventing undesirable flow patterns such as the pre-rotation, retrograde flow, and inlet circulation from occurrence at the design and off-design conditions. Because splitter blades take some percentage of pressure loading from the principle blades, it makes the pressure distribution more uniform along the entire blade region and especially on the outlet side of the impeller blades and stator blades at all operating conditions. Therefore, the flow at the outlets of the impeller and stator blades becomes difficult to separate. Outflow circulation and vortices are further prevented from occurrence. All these improvements in flow field and pressure distribution result in an increased pump efficiency. The higher efficiency provides the benefit of low temperature rise of the motor and longer battery life. As contact with bodily tissues is inherent, the reduction in operating temperatures minimizes related trauma to surrounding body tissues.

Red blood cell damage in blood pumps is mainly related to the shear stress and exposure time of the red blood cells passing through the flow paths. A uniform flow field without separation and vortices due to the consideration of splitter blades leads to a low shear stress and short exposure time. Among other things, embodiments of the present invention device address such issues. Embodiments of the present invention further provide smooth operation at design and off-design conditions because the configuration of the splitter blades fitted into the impeller and stator can, to a great extent, prevent from occurrence of undesirable steady and unsteady flow patterns such as the separation, inlet pre-rotation, retrograde flow, inlet and outlet circulation, and surge as well.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

FIG. 1 is a longitudinal cross-sectional (meridional) view of a pump in accordance with an embodiment of the present invention;

FIG. 2 is a perspective view of various components of the pump shown in FIG. 1;

FIG. 3 is perspective view of various components of the pump shown in FIG. 1 including with a partial cross-sectional view of a housing member;

FIG. 4 is a front axial view of the impeller of the pump shown in FIG. 1;

FIG. 5 is a rear axial view of the stator blades of the pump shown in FIG. 1;

FIG. 6 is a longitudinal cross-sectional (meridional) view of a pump in accordance with another embodiment of the present invention; and

FIG. 7 is a perspective view of various components of the pump shown in FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments are described more fully below in sufficient detail to enable those skilled in the art to practice the system and method. However, embodiments may be implemented in many different forms and the present invention should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken to be limiting in any sense. For purpose of illustration, discussions of the invention will be made in reference to its utility as a cardiac assist blood pump. However, it is to be understood that the technology may have a variety of wide applications to many types of turbomachinery including, for example, commercial and industrial pumps, compressors, and turbines.

Referring to FIGS. 1 through 5, a rotordynamic blood pump 100 is shown in accordance with an embodiment of the present invention. FIG. 1 shows a meridional section of the pump 100. FIG. 2 shows a perspective view of various components of the pump, the housing of the pump being removed from the view for purposes of clarity. FIG. 3 shows a perspective view of the pump 100 with the housing being sectioned to provide context to other components of the pump 100. FIGS. 4 and 5 are end views, depicting impeller blades and stator blades, respectively.

The pump 100 includes a stator housing 102 having an inlet 104 and an outlet 106. A rotor hub 108 having a generally cylindrical configuration is disposed within the stator housing 102 forming a clearance gap or an annulus 110 between rotor hub 108 and stator housing 102. The rotor hub 108 includes a leading portion 112 (i.e., leading with respect to intended fluid flow through the pump 100) that exhibits a generally conical geometry and that is positioned near the inlet 104. Additionally, the rotor hub 108 includes a trailing portion 114 (i.e., trailing with respect to intended fluid flow through the pump 100) that exhibits a generally conical geometry and that is positioned near the outlet 106.

The pump 100 includes a mixed-flow (or high-specific speed centrifugal) type impeller with principle impeller blades 116 of a first length and shorter splitter blades 118. The principle and splitter blades 116 and 118 may be positioned, for example, on the leading portion 112 of the rotor hub 108. The leading edge of the splitter blades 118 is staggered behind (or placed axially downstream of) the leading edge of principle blades 116 but axially upstream relative to the trailing edge of the principle blades 118 so that the splitter blades 118 overlap at least a portion of principle blades 116 in meridional section or along the axial flow path. In the embodiment shown in FIG. 1, the impeller blades (both principle 116 and splitter 118) are unshrouded. Such a configuration may provide cost savings and reduce the complexity of manufacturing. However, shrouded configurations are also contemplated herein as will be discussed below. In the unshrouded configuration shown in FIGS. 1-5, blade tip clearances or gaps are exhibited between the lengthwise radial outward surfaces of the rotating impeller blades 116 and 118 and the inner surface of the stationary stator housing 102.

Downstream of impeller blades 116 and 118, stator vanes are positioned near the outlet 106 adjacent the trailing portion 114 of the rotor hub 108. The stator vanes include principle vanes 120 and shorter splitter vanes 122 which extend radially inward from the stator housing 102. The stator vanes 120 and 122 help to recover kinetic energy of the fluid (e.g., blood) and lead the fluid to flow axially through the outlet 106. The leading edge of the splitter vanes 122 is staggered behind, or positioned axially downstream from, the leading edge of principle vanes 120. The trailing edge of both principle stator vanes 120 and splitter stator vanes 122 terminate at approximately the same meridional or axial position. There are blade tip clearances or gaps between the lengthwise lower surface of the stator vanes 120 and 122 and the rotating rotor hub 108. The extent of both blade tip clearances and the vane tip clearances can have significant effects on the pump's performance including, for example, pump head and efficiency. Additionally, these clearances can have a significant impact on the amount of damage that may occur to the blood cells. In one particular embodiment, both the impeller blade tip clearances and the stator vane tip clearances are may be approximately 0.1 mm to approximately 0.2 mm. However, the clearances may be set at other distances depending on a variety of factors as will be appreciated by those of ordinary skill in the art.

In one particular embodiment, the ratio of the averaged streamline-wise meridional length of the splitter stator vanes 122 to that of principle stator vanes 120, as well as the impeller splitter blades 118 to the impeller principle blades 116, is approximately 0.6 to approximately 0.75. In other words, the axial length of a splitter stator vane 120 is approximately 0.6 to approximately 0.75 as long as the axial length of a principle stator vane 120 (and likewise for the splitter impeller blades 118 relative to the principle impeller blades 116).

It is noted that both the radial clearance and the axial length of the annulus 110 or annular gap can have a significant effect on pump performance and possible blood damage. For a magnetically suspended and rotated blood pump, the sizing of the annulus 110 also has an effect on the radial and yaw stiffness of the suspension system. From a point view of hydrodynamics, the radial gap of the annulus 110 should be made as large as reasonable possible, while for the consideration of magnetic suspension system, the radial gap of the annulus 110 should be small enough, and the axial length of the annulus 110 should long enough, to maintain a stable rotation of the rotor hub 106 within the stator housing 102.

It is noted that the components of the pump 100 are shown in relatively simplistic forms for sake of clarity in the associated description. For example, the magnetic and electronic components that might be utilized in association with a magnetic levitated pump are not specifically shown. However, one of ordinary skill in the art will recognize that such components will be inherently placed in or adjacent to the stator housing 102 and within the rotor hub 108 to provide such a magnetically levitated pump. One example of a completely magnetically suspended system associated with a pump is described in U.S. Patent Application Publication No. 20110237863 entitled MAGNETICALLY LEVITATED BLOOD PUMP WITH OPTIMIZATION METHOD ENABLING MINIATURIZATION, the disclosure of which is incorporated by reference herein in its entirety.

In one particular embodiment, such as seen in FIGS. 1-5, the impeller may include three (3) principle blades 116 and three (3) splitter blades 118 spaced between occurrences of principle blades 116. Thus, these mixed-flow (or high-specific speed centrifugal) type blades are arranged alternatively in circumferential pattern about the about of the rotor hub 108. Additionally, in accordance with this embodiment, the stator vanes may include three (3) principle stator vanes 120 and three (3) splitter vanes 122 arranged spaced between the principle vanes 120 in a circumferential alternating pattern. The rotating impeller blades 116 and 118 and the stationary stator vanes 120 and 122 may each exhibit 3-dimensional curved surfaces designed, for example, using conventional turbomachinery inverse design theory such as 2D or quasi-3D methods. Additionally, their shapes and numbers (i.e., greater of fewer than three of a give blade or vane) may optimized via computational fluid dynamics (CFD) to reach a desired efficiency with minimal blood damage.

In one embodiment, the trailing edge of the splitter blades 118 (i.e., the edge closer to the outlet 106) may axially coincide with the trailing edge of the principle blades 116. Similarly, the trailing edge of the splitter vanes 122 may axially coincide with the trailing edge of the principle vanes 120. Also, the trailing edge angles of the splitter blades 118 may exhibit substantially the same angle as the trailing edge of the principle blades 116. Likewise, the trailing edge angles of the splitter vanes 122 may exhibit substantially the same angle as the trailing edge of the principle vanes 120. However, the positions and trailing edge angles of the splitter blades may be optimized by CFD.

As noted above, the leading edge position of the splitter blades 118 (or splitter vanes 122) may generally axially staggered downstream of the leading edges of the principle blades 116 (or principle vanes 120). The circumferential positions and the leading edge angles of the splitter blades 118 (or splitter vanes 122) may be determined by inverse design methods and CFD optimization so that the pressure loading in both the splitter blades 118 (or splitter vanes 122) and the principle blades 116 (or principle vanes 120) is uniform. The principle stator vanes 120 may be designed so that the leading edge angles generally match the flow out of impeller blades 116 and 118. The trailing edge angles of both the principle vanes 120 and splitter vanes 122 may be approximately 90° so that the blood can be led to the outlet 106 uniformly and smoothly without much turbulence. The geometry of the converging trailing portion 114 of the rotor hub, along with the stator vanes 120 and 122 may be designed and optimized by CFD to further recover potential energy (pressure) from the kinetic energy of the fluid flow.

With more particular reference to FIG. 4, an end view of the impeller blades 116 and 118 is shown. Because the leading edge of the splitter blades 118 is axially staggered behind or downstream of the principle blades 116 in a radial spaced apart relationship, the blockage due to the simultaneous introduction of numerous blades in the impeller inlet region is reduced significantly so that higher mass flow can be passed through the impeller region more smoothly. Also due to the blade loading taken by the splitter blades 118, pressure distribution and uniformity of flow fields in outlet side may be improved considerably. Although the principle blades 116 can be designed initially by the conventional turbomachinery inverse design theory and then optimized by CFD, there is no established theory for the initial design of the splitter blades 118 regarding, for example, their positions, blade loading, leading edge and trailing edge angles, and wrap angles. As such, the shapes, positions, and profiles of the splitter blades 2 a may be optimized by advanced CFD to make sure that the pressure and flow velocities distribute uniformly and smoothly with high pump efficiency and minimal blood damage.

With more particular reference to FIG. 5, a rear axial view of the stator vanes 120 and 122 is shown. Unlike most industrial pumps, where the hub 108 or the transitional converging region is usually stationary, for magnetically suspended and rotated blood pumps, the converging region exhibited by the trailing portion 106 rotates with the rotor hub 108 (i.e., see FIG. 1). Due to the effect of centrifugal force, the rotating trailing portion 114 generates a flow field and an adverse pressure gradient against the main flow passing through the stator vane region. Because of this interaction, the flow becomes much more easily separated and is more prone to surging than in more conventional industrial pumps. Separated blood flow can generate recirculation and vortices, which not only deteriorate the pump performance, but also increase the risk of blood damage. The inclusion of the splitter vanes 122 can take some blade loading from principle vanes 120 and compensate the adverse pressure gradient generated by the rotating converging trailing portion 114 of the rotor hub 108 so as to avoid, or at least minimize, flow separation and to generate a more uniform pressure and flow field than in configurations without splitter vanes 122.

Referring briefly to FIGS. 6 and 7, a pump 100′ is shown in accordance with another embodiment of the present invention. The pump 100′ is configured substantially similarly to that described above with respect to FIGS. 1-5, including a stator housing 102 having an inlet 104 and an outlet 106. A rotor hub 108 having a generally cylindrical configuration is disposed within an interior volume defined by the housing such that an annulus 110 or annular gap exists between the rotor hub 108 and the stator housing 102. The rotor hub 108 includes a leading portion 112 that exhibits a generally conical geometry and that is positioned near the inlet 104. Additionally, the rotor hub 108 includes a trailing portion 112 that exhibits a generally conical geometry and that is positioned near the outlet 106. The pump 100′ further includes impeller blades associated with a mixed-flow stage that are formed on, or otherwise coupled with, the rotor hub 108 along the leading portion 112 (i.e., in the conical region). The impeller blades include principle blades 116 and shorter splitter blades 118. Downstream of the impeller blades 116 and 118, adjacent the pump outlet 106 and the trailing portion 114 of the rotor hub 108, a plurality of stator vanes, including principle vanes 120 and splitter vanes 122, extend radially inward, such as from an inner surface of the stator housing 102.

The difference from the embodiment described with respect to FIGS. 1-3 is the inclusion of a front shroud 124 associated with the impeller blades 116 and 118. The shroud 124 includes solid surface that circumferentially encloses the radially outer ends of the impeller blades 116 and 118. A clearance gap is defined between the radial outer surface of the shroud 124 and the inner surface of the stator housing 102. An advantage of the shrouded blades is the elimination of blade tip leakage and the corresponding hydraulic losses that occur in an unshrouded configuration. The inclusion of a front shroud 124 can also increase the mechanical strength of the impeller and may act as a damping touchdown for the magnetically suspended and rotated rotor hub 108. However, the use of shrouded blades can induce the disk friction losses with a very complex retrograde flow pattern, possibly increasing the risk of blood damage. The use of a front shroud 124 may also increase the complexity and cost of the manufacturing, especially for systems comprising mixed-flow type impeller blades that are of miniature size.

The pumps and components formed herein may be formed using a variety of manufacturing techniques as will be appreciated by those of ordinary skill in the art. Some examples of techniques that may be used in manufacturing pumps and components of the present invention are set forth in U.S. patent application Ser. No. 12/XXX,XXX (attorney docket number 52722.0108), entitled BLOOD PUMP WITH SEPARATE MIXED-FLOW AND AXIAL-FLOW IMPELLER STAGES COMPONENTS THEREFOR AND RELATED METHODS, filed on even date herewith, the disclosure of which is incorporated by reference herein in its entirety. Additionally, the incorporated application includes non-limiting examples of pump dimensions that are applicable to the present invention for certain embodiments.

While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims. It is specifically noted that any features or aspects of a given embodiment described above may be combined with any other features or aspects of other described embodiments, without limitation. It is also noted that features set forth in association with the embodiments expressly described herein may be combined with features set forth in the various documents previously incorporated by reference without limitation. 

1. A pump for delivering continuous flow of fluids, comprising: a stator housing having an inlet and an outlet; a rotor hub disposed within the stator housing between the inlet and the outlet, the rotor hub comprising a body having a leading portion position adjacent the inlet, a trailing portion positioned adjacent the outlet, and at least one impeller blade positioned at the leading portion; at least one principle stator vane extending radially inward from the stator housing and positioned between the inlet and outlet; and at least one splitter vane positioned adjacent the at least one principle stator vane, the at least one splitter vane exhibiting an axial length that is shorter than the at least one principle vane.
 2. The pump of claim 1, wherein the at least one principle stator vane includes a plurality of principle stator vanes, wherein the at least one splitter vane includes a plurality of splitter vanes, and wherein the plurality of principle vanes and the plurality of splitter vanes are arranged in a circumferentially alternating pattern.
 3. The pump of claim 2, wherein at least one impeller blade includes a plurality of impeller blades configured to provide both centrifugal flow and axial flow to fluid flowing therethrough.
 4. The pump of claim 3, wherein the plurality of impeller blades includes at least one principle blade and at least one splitter blade, the at least one splitter blade being axially shorter than the at least one principle blade.
 5. The pump of claim 4, wherein the at least one principle blade includes a plurality of principle blades, wherein the at least one splitter blade includes a plurality of splitter blades, and wherein the plurality of principle blades and the plurality of splitter blades are arranged in a circumferentially alternating pattern.
 6. The pump of claim 5, wherein a leading edge of each of the plurality of splitter vanes is positioned axially closer to the outlet than a leading edge of each of the plurality of principle vanes.
 7. The pump of claim 6, wherein a leading edge of each of the plurality of splitter blades is positioned axially closer to the outlet than a leading edge of each of the plurality of principle blades.
 8. The pump of claim 7, further comprising a shroud coupled with and at least partially enclosing the plurality of principle blades and the plurality of splitter blades.
 9. The pump of claim 6, wherein the plurality of principle blades includes three principle blades and wherein the plurality of splitter blades includes three splitter blades.
 10. The pump of claim 9, wherein the plurality of principle vanes includes three principle vanes and wherein the plurality of splitter vanes includes three splitter vanes.
 11. The pump of claim 6, wherein a trailing edge of each of the plurality of the principle blades axially coincides with a trailing edge of each of the plurality of splitter blades.
 12. The pump of claim 11, wherein a trailing edge of each of the plurality of the principle vanes axially coincides with a trailing edge of each of the plurality of splitter vanes.
 13. The pump of claim 6 wherein the rotor hub is configured to be magnetically suspended and rotated within the stator housing.
 14. The pump of claim 13, wherein the stator housing, the rotor hub, the plurality of principle stator vanes and the plurality of splitter stator vanes comprise blood compatible materials.
 15. The pump of claim 1, wherein the at least one principle vane and the at least one splitter vane are integrally formed in the stator housing.
 16. A pump for delivering continuous flow of fluids, comprising: a stator housing having an inlet and an outlet; a rotor hub disposed within the stator housing between the inlet and the outlet, the rotor hub comprising a body having a leading portion position adjacent the inlet, a trailing portion positioned adjacent the outlet, a plurality of principle impeller blades, and a plurality of splitter impeller blades, each of the plurality of splitter blades being axially shorter than each of the plurality principle blades, the plurality of splitter blades and the plurality of principle blades being arranged in an alternating circumferential pattern about the leading portion of the body; a plurality of principle stator vanes extending radially inward from the stator housing and positioned between the inlet and outlet; and a plurality of splitter stator vanes extending radially inward from the stator housing, each of the plurality of splitter vanes exhibiting an axial length that is shorter than each of the plurality of principle vanes.
 17. The pump of claim 16, wherein the rotor hub is configured to be magnetically suspended and rotated within the stator housing.
 18. The pump of claim 13, wherein the stator housing, the rotor hub, the plurality of principle stator vanes and the plurality of splitter stator vanes comprise blood compatible materials.
 19. A method of manufacturing a pump, the method comprising: providing a stator housing having an inlet and an outlet; providing a rotor hub having a mixed-flow impeller near a leading portion of the rotor hub; positioning the rotor hub within the stator housing to define an annular flow path through the stator housing; providing at least one principle stator vane extending from the stator housing; providing at least one splitter stator vane extending from the stator housing adjacent the at least one principle stator vane, the at least one splitter vane having an axial length that is shorter than the at least one principle vane.
 20. The method of claim 19, further comprising configuring the mixed-flow impeller to include at least one principle impeller blade and at least one splitter impeller blade, the at least one splitter blade having an axial length that is shorter than the at least one principle blade.
 21. The method of claim 20, further comprising magnetically suspending the rotor hub within the stator housing. 